The invention relates to a gear arrangement, and in particular, to a gear arrangement for use in connection with motor vehicle window lifter drives.
In the worm gear arrangement known from DE-GM 84 27 394 and used in a motor vehicle window lifter drive, the window pane is driven at full force into its "window closed" and "window open" end positions by the drive motor. To cushion the shock loads acting upon the motor and the other drive assembly components during this process, a rubber cushioning disk is inserted between the gear driven by the motor shaft via a worm and mounted in the gear box and an axially preceding dog plate coupled to the output shaft. The rubber cushioning disk absorbs the shock in the radial and tangential directions when the motor arrives in the above described end positions.
The output shaft is rotatably mounted in the gear box and supported in one axial direction by an output pinion and in the other axial direction by the dog plate. The other components of the cushioning disk and the gear arrangement sit on the output shaft in the gear box. Due to the tolerances of the parts of the assembled components, in each individual case care must be taken during assembly that, on the one hand, axial jamming and operating stiffness are avoided at maximum plus tolerances and, on the other hand, vibratory and running noises are avoided at maximum minus tolerances. In the known case one has attempted, therefore, to provide tolerance compensation by the interposition of appropriate shims or Belleville washers, depending on the total tolerance measured first in each individual case.
It is an object of the present invention to be able to produce the components with the tolerances usual for mass production and assure, despite simple, especially readily automated, assembly, great functional reliability and long life of the gear arrangement, particularly taking into account the wide operating temperature differences given in a window lifter drive application.
The object of the invention is achieved in a gear arrangement of the above described type wherein the output shaft is rotatably mounted in a gear box and co-rotates via an axially interposed elastic cushioning disk with a gear driven by a drive shaft. The output shaft is supported directly or indirectly by the gear box by means of the cushioning disk. A predefined preloading pressure upon the components of the gear arrangement is provided by axially projecting spring lips distributed circumferentially over the surface of the elastic cushioning disk.
Due to the cushioning element design according to the invention, it is possible to eliminate the manufacturing steps of having to measure separately the cumulative tolerance in each individual case and having to insert separately one or more shims or Belleville washers because, on the one hand, the spring lips can be made to be an integral part of the cushioning disk and are, therefore, assembled with the latter and, on the other hand, if the axial pressure remains approximately the same, the different axial tolerances can be compensated through the deformation of the spring lips when assembling those components which are to be under a defined preload. On the one hand, the compression or squeeze generated when mutually bracing the components axially against the gear box due to the deformation of the spring lips is so great that sufficient axial bracing of the parts is still assursed at maximum tolerance play and, on the other hand, if the resultant play is minimal, the compression of the assembled parts is not yet so great that it becomes difficult for the motor drive to turn the parts it is designed to drive or that jamming of these parts occurs.
By changing the axial height, the profile and/or the distribution of the spring lips on the one face of the cushioning disk it is possible to adapt, in a simple manner, to different designs or preloads. If the spring lips are arranged so as to extend tangentially, especially near the outer peripheral surface of the cushioning disk, it is additionally possible in an advantageous manner, to prevent tilting of the gear, which is rotatably mounted on the output shaft with relatively large radial play to take into account the great operating temperature differences. This is due to the fact that the spring lip support is located far on the outside of the dog plate of the gear arrangement, thus assuring optimal engagement of the worm shaft driving the gear while keeping friction and wear low.